As the materials for propagation and education, materials of a three-dimensional image have been used. The three-dimensional image is useful because the image not only gives plane visual information but also gives three-dimensional information by the shades and the feeling of finger and give a strong impression and understanding. As the particularly effective using manner, there are Braille types and Braille images. The three-dimensional image is used not only as language information but also image information such as a map, etc., and are indispensable for a blind person.
As a method of forming a three-dimensional image, following method have hitherto been known.
For example, for the preparation of Braille types, etc., a method of forming projections on the surface of a paper by embossing working using a type writer for Braille type has been widely used. Also, as a method of duplicating a three-dimensional image and preparing a Braille book, etc., there is a method of using a zinc sheet having formed thereon Braille images by the same principle as the above-described type writer for Braille type as the original plate and duplicating the Braille images using a Braille type plate-making machine or a Braille printing machine. Also, as a method of preparing pamphlets, etc., of a three-dimensional image, there is a method of convexly printing using a ultraviolet-curing high-viscosity polymer ink by utilizing a printing technique such as an ordinary silk screen, etc., but the method is not a method which can be simply used in general offices, etc.
The three-dimensional image forming methods of the related art described above have the faults that a long time is required and further the using place is limited. Furthermore, in the case of duplicating a three-dimensional image, the process of making duplicates and the apparatus used therefor are complicated and become a large scale and the method is unsuitable for the present information-oriented society. Recently, office instruments have been greatly progressed and in particular, by the progress and spreading of personal computers, the preparation of material becomes quick and easily and the output instruments are being attained small sizing, light weighting, cost lowering, high speeding, and coloring thereof. Also, about the three-dimensional image, the development of the instrument capable of easily outputting and duplicating a three-dimensional image has been desired. In particular, if it becomes possible to obtain at a low cost a software capable of converting ordinary letters (plane letter) into Braille letters or reverse converting of them, the participation of blind persons to society can be further accelerated. Also, to expand the possibility of the exchange of electronic mails in blind persons each other, an output apparatus capable of easily outputting Braille letters, etc., is necessary.
That is, it is the actual situation that in the output and the duplicate of a three-dimensional image, the development of an easy and high-speed system corresponding to the office environment at present has been desired in place of a conventional complicated and large system.
On the other hand, in JP-A-8-60054, an ink jet ink containing a ultraviolet decomposition type gas-generating photosensitive compound, and apparatus using the ink, and a method of forming a three-dimensional image using it are proposed. Because the output apparatus disclosed in the specification of the above-described patent application is a small-sized apparatus and also the output from a personal computer is possible, the method proposed is an effective method of forming a three-dimensional image. However, there is a problem that when a three-dimensional image is intended to output on a plain paper, the liquid ink permeates into the fibers of the paper and when the images are expanded with ultraviolet rays, sufficient a three-dimensional image is not obtained. Accordingly, it is proposed to use a non-liquid-absorbing recording material such as PET, etc., but the use of such a material is expensive and is unsuitable for bookbinding, whereby the practical use is difficult.
Thus, as a method of easily forming a three-dimensional image, a method of using an electronic photographic system which is widely used in offices and for personal computers has been proposed. For example, in JP-B-59-35359 and JP-A-61-72589, a method of using a thermally expanding sheet is proposed. This is the method of uniformly coating a thermally expanding material on a support such as a paper, etc., and thermally expanding the imaged portions only to prepare a three-dimensional image. According to the method, an ordinary copying machine can be utilized, the thermally expanding sheet is used in place of an ordinary plain paper, images of a black toner are formed on the sheet, and the thermally expanding material under the toner images are expanded by utilizing the heat-absorbing property of the black toner to form a three-dimensional image. This method is preferred in the point of easily forming a three-dimensional image but is not preferred from the points that a black toner is required for sufficiently thermally expanding the thermally expanding material, other heating apparatus is required, a considerably long time is required to form a three-dimensional image having a sufficient image thickness, and further it is necessary to coat the thermally expanding material on the whole surface of the sheet, which is against the requirement of resource saving. Moreover, the sheet is thick, which is unsuitable to bookbinding using many sheets, and thus it is difficult to use the method for practical purpose.
On the other hand, in JP-A-4-333858 and JP-A-8-63039, a method of using a conventional electrophotographic system and forming a three-dimensional image by increasing the amount of the toner on the images is proposed. However, because the method is a method of increasing the height of the images by forming the toner images using a large amount of a conventional toner, there is a problem that fixing of the toner to a paper, etc., becomes insufficient and, on the other hand, when fixing is carried out at a high temperature to make fixing sufficient, the toner is melted and permeates into the fibers of the paper, whereby the height of the images becomes insufficient.
Furthermore, in JP-A-52-28325, an electrophotographic toner containing a dry intumescing agent is proposed. In the method, a toner obtained by powder-mixing a conventional toner and the above-described intumescing agent is used and after image forming, the dry intumescing agent is expanded by heat to obtain a three-dimensional image. However, because by powder-mixing, the toner and the intumescing agent cannot be sufficiently uniformly mixed, it frequently happens that the intumescing agent without having an adhesive force exists at the boundary surface of toner and the paper, whereby the a three-dimensional image having a sufficient fixing property are not obtained. Also, because the adhesive property of toner particles and the intumescing agent is insufficient, to increase the adhesive property, a method of incorporating the dry intumescing agent in the toner (in this case, the intumescing agent incorporated in the toner intumesces by heat-kneading at the preparation of the toner, whereby the agent loses the thermal expanding property) and further powder-mixing the toner with the remaining dry intumescing agent to improve the adhesive property of the toner particles and the intumescing agent is proposed. However, by the method, the adhesive property of the paper and the toner is not improved and the fixing property of the images and the paper is yet insufficient. Also, because in general, the electrostatic charging property of a binder resin is different from that of the dry intumescing agent, from the difference in the electrostatic charging property, the charge distribution of the toner becomes wide and with the change of an environment, the quality of the images obtained is lowered by using the toner for a long period of time.
Also, in JP-A-7-061047, an inlet and outlet method of information for forming projected images using a toner containing a heat-sensitive foaming agent is proposed. The toner used in the method is prepared by mixing a binder resin for toner, a coloring agent, and a heat-resisting foaming agent and finely grinding the mixture and the heat-sensitive foaming agent is exposed on the surface of the ground toner, whereby there is a portion of existing the heat-resisting foaming agent at the boundary surface of the paper and the toner as the in the case of the above-described method, the adhesive property of the toner and the paper is lowered, and the fixing property of the images made of the above-described toner is inferior. Also, because the heat-resisting foaming agent is exposed on the surface of the toner, the electrostatic charging property on the surface of the toner become nonuniform. Accordingly, the electrostatic charge distribution of the toner becomes wide and when the toner is used under a low-temperature low-humidity environment or when the toner is used for a long period of time, quality lowering such as the occurrence of fog, etc., on the images occurs. Also, because the toner used is prepared by an ordinary kneading and grinding method, it is considered that the greater part of the heat-resisting foaming agent lose the effect by the heat at kneading. As the result thereof, because the foaming agent cannot be sufficiently expanded by heat fixing only of an ordinary copying machine, etc., it is necessary to pass the outputted images through other heating apparatus, and thus the method is insufficient in the point of simplicity.
As described above, it is the actual circumstances that a toner capable of easily forming a three-dimensional image by a copying machine or a small-sized printer (without need of other heating apparatus, etc., and without need of substantial reconstruction) of an ordinary electrophotographic system does not exist. Also, it is the actual circumstances that a toner capable of easily forming images having the image height which can be sufficiently recognized as Braille type and also having a good fixing property even on a plain paper does not exist. Furthermore, it is the actual circumstances that an image-forming toner having a sufficiently good productivity for practical use, an electrostatic charging uniformity, and an environmental stability does not exist.